Another fascinating pathway followed was ‘cold welding’, where, under vacuum, in the absence of heat, the crystal structure of a metal will merge with an adjacent, similar crystal structure. It is very counterintuitive, and only emerged in the 60’s in association with spacecraft, out of a dreadful experience in the early Gemini program, where a door could not be shut after a spacewalk. In this case, the door hinges had started to ‘cold weld’. Another example was the failure of a solar ‘umbrella’ to open as the stays cold welded together. So great care is taken in modern spacecraft to ensure no direct contact between similar metals. In a crankshaft application, its all about grain flow, determined in the original forging process. So the theory is that cold welding does not disturb the original grain flow. In theory, you could centrifugally cast identical crankshaft alloy into sleeves, creating a linear grain flow in the sleeve, which would be ideal in a ‘journal surface’. This machined sleeve could then be clamped to a prepared, cleaned, old journal, and the lot put in a vacuum chamber. After a few weeks, the join between the new sleeve and the old journal surface might be indistinguishable. I can’t think of a better way to preserve the original grain flow in the crankshaft while building up the journal surface to ‘as new’. Only way to find out is to try. Another option is fine laser engraving of the new journal surface for optimum oil holding properties.
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